She can take it easy, mostly. No D or F grades. A whole bunch of C’s might be a problem at some schools.
I had a student last year who “developed” senioritis. Several of his grades slipped to C’s. This prompted an email from the college asking him to explain the lower grades. The college wasn’t messing around. It was a pretty selective LAC. They were satisfied with his explanation, but I think the real purpose of the email was to put him on notice that they expected him to perform.
It’s not that hard to maintain good grades. A C or two, a few B’s are not usually a problem.